The binding of NMO patient-derived antibodies to the extracellular domains of AQP4 initiate an immune-mediated pathology that is characterized by activation of complement, astrocyte cytotoxicity, inflammation with granulocyte infiltration, and oligodendrocyte cell death leading ultimately to demyelination (3, 6, 17, 18). This evidence concerns the gene AQP4 and neuromyelitis optica.